As one type of plating apparatus there is available a cup-shaped plating apparatus 100 used for the plating of wafers etc. As shown in FIG. 6, the cup-shaped plating apparatus 100 is provided with a plating tank 101 and a wafer placement portion 106 in a top opening of the plating tank 101. Within the plating tank is provided an anode (a positive electrode) 105, which is one electrode for electrolytic plating. Also, a cathode (a negative electrode) which is the other electrode for the same, a silver packing 107, etc. are attached to the placement portion 106. That is, when a wafer W is placed on the placement portion, a plating target surface Ws of the wafer W is brought into contact with a plating solution within the plating tank and a current is caused to flow between the two electrodes in this state, the target surface Ws is subjected to plating treatment.
This cup-shaped plating apparatus has a plating-solution-supply tube 102 connected to the bottom of the plating tank 101 and an outlet pore 104 formed in a side wall 103 of the plating tank 101 near the top opening of the plating tank, which outlet pore 104 leads to a cavity 108 within the side wall 103, and an then to an outlet 109 leading out of the apparatus. Therefore, it is possible to perform plating treatment while continuously supplying a fresh plating solution from the supply tube 102. The plating solution thus supplied flows toward the plating target surface in an upward current and flows thereafter to the outer peripheral side of the plating tank in a radially spreading pattern (refer to the Japanese Patent Application Laid-Open No. P2002-173794).
Performing plating treatment while continuously supplying a plating solution in this manner provides advantages, for example, it is possible to perform plating treatment more rapidly.
However, when plating treatment is performed during the continuous supply of a plating solution, nonuniform plating attributable to the flow of the plating solution may sometimes occur. Particularly, in the outer peripheral portion of a plating target surface of a wafer near the side wall of the plating tank, nonuniform plating and variations in plating, such as a larger plating film thickness than in the middle portion of the plating target surface, are apt to occur.
The present invention was made against a background as described above and has as its problem the provision of a cup-shaped plating apparatus which ensures that the whole area of a plating target surface is subjected to plating with a uniform film thickness.